This study aims to quantitatively define the changes in the scalp recorded EEG in male volunteer subjects receiving single and multiple doses of phenytoin (diphenylhydantoin, Dilantin), and to relate these to behavioral and blood level measures. The study is designed to develop quantitative measures of cerebral changes for use in clinical studies of the efficacy of phenytoin in epilepsy and neuropsychiatric disorders. The EEG measures will be power spectral density analysis and period analysis using digital computer methods. Blood levels will be done by gas-liquid chromatography. Behavior will be assessed using established and newly developed behavior and symptom rating scales.